Plotting wind direction as arrows with precipitation

Thanks Bert,
I think that arrow()  would do what the OP needs. The main problem would
be calculating the angles properly if I understand the issue. Still there
cannot be "that" many points on a compass, can there?

John Kane
Kingston ON Canada

-----Original Message-----
From: bgunter.4567 at gmail.com
Sent: Tue, 11 Aug 2015 07:55:55 -0700
To: jrkrideau at inbox.com
Subject: Re: [R] Plotting wind direction as arrows with precipitation

... don't know if this will help, but grid graphics, which is the
graphics engine for both trellis and ggplot, has a basic arrow()
function. Trellis's provides an interface to it with the
panel.arrows() panel function. I suspect ggplot has something similar,
but as I don't use it, I don't know for sure.

There is also an arrows() function in the basic (non-grid) graphics
engine, but this is probably irrelevant for your needs.

Cheers,
Bert


Bert Gunter

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
   -- Clifford Stoll


On Tue, Aug 11, 2015 at 7:16 AM, John Kane <jrkrideau at inbox.com> wrote:

Hi,
Good example and data.  Thanks.

Here are a couple of approaches that may help.
I tend to use a lot of what I tend to think of as the ggplot family of
associated so you may need to install a couple packages. I used
lubridate to transform your character dates to  POSIXct. Jeff N's code
does exatly the same in base R. so you don't really need the lubridate
package.

 I changed the data set name to dat1 and transformed the column names to
lower case just for my convenience.  Data is now in dput() form. See
?dput() for more information. It is the preferred way to share data on
R-help

Given what appears to be vastly different y-scales for rainfall and wind
direction it struck me that it might be better to have the data in two
plots so I included that option.

I am not really sure how to get the arrows you want. You may be able to
do it using scale_shape_manual  but I am not sure if the required
symbols are available.

You may have to manually draw them. See

http://stackoverflow.com/questions/3421331/example-needed-using-arrow-with-ggplot2

for how to draw an arrow.

John Kane
Kingston ON Canada
##============Start code==============
library(ggplot2)
library(reshape2)
library(lubridate)
library(gridExtra)

dat1  <-  structure(list(deal1 = c("10/22/2012 0:00", "10/22/2012 0:15",
"10/22/2012 0:30", "10/22/2012 0:45", "10/22/2012 1:00", "10/22/2012
1:15"
), rainfall_cm = c(0L, 0L, 0L, 0L, 0L, 0L), wind_direction1 = c(296L,
317L, 323L, 323L, 326L, 326L), wind_direction2 = c("W", "NW",
"NW", "NW", "NW", "NW")), .Names = c("deal1", "rainfall_cm",
"wind_direction1", "wind_direction2"), class = "data.frame", row.names =
c(NA,
-6L))


dat1$deal1 <- mdy_hm(dat1$deal1) # Lazy man's equivalent of Jeff N's
Sandy$Deal1 <- as.POSIXct( Sandy$Deal1, format="%m/%d/%Y %H:%M")

dat2  <-  melt(dat1[ , 1:3], id.var = "deal1")  # use reshape to
rearrange data.
p  <-  ggplot(dat2, aes(deal1, value, colour = variable) )+ geom_point()
p

## possible option
g1  <-  ggplot(dat1, aes(deal1,  wind_direction1)) + geom_point() +
theme(axis.title.x=element_blank())
g2  <-  ggplot(dat1, aes(deal1, rainfall_cm ) )+ geom_point()

grid.arrange( g1, g2, ncol=1)

##===========end code==================

-----Original Message-----
From: rhelp10 at gmail.com
Sent: Mon, 10 Aug 2015 00:05:27 -0400
To: r-help at r-project.org
Subject: [R] Plotting wind direction as arrows with precipitation

Hello R users!

I am trying to create a time series in R with two variables,
precipitation
and wind direction vs Date/Time.

I am looking for suggestions and maybe even sample code.

My workbook is called "Sandy" and has columns with Date/Time,
Raindall_cm,
Wind Direction in both degree format (0-359) and in character form (N,
NW,
S, SW, SE, E, NE, NW).

I have done some reading for it on stackoverflow and other sites but
not
making head way.

I will be graphing with ggplot most likely and am a beginner in R, self
taught from books and online resources.

This is the code I have and a small peak into the data.

Sandy<-read.csv("Sandy.csv", header=TRUE,
sep=",",stringsAsFactors=FALSE)

head(Sandy)

      Deal1     Rainfall_cm    Wind_Direction1 Wind_Direction2
1 10/22/2012 0:00           0        296         W
2 10/22/2012 0:15           0        317        NW
3 10/22/2012 0:30           0        323        NW
4 10/22/2012 0:45           0        323        NW
5 10/22/2012 1:00           0        326        NW
6 10/22/2012 1:15           0        326        NW

class(Sandy)

[1] "data.frame"

str(Sandy)

'data.frame':   1832 obs. of  4 variables:
 $ Deal1         : chr  "10/22/2012 0:00" "10/22/2012 0:15" "10/22/2012
0:30" "10/22/2012 0:45" ...
 $ Rainfall_cm   : num  0 0 0 0 0 0 0 0 0 0 ...

 $ Wind_Direction: num 296 317  323   323  326  326

 $ Wind_Direction: chr  "W" "NW" "NW" "NW" ...

require(ggplot2)

Loading required package: ggplot2

# this graph does the precipitation vs time graph, but not the wind

ggplot(Sandy, aes(x = Deal1, y = Rainfall_cm, group = 1)) +

geom_line(stat = "identity")


Ideally I want it to have the precipitation graph vs time, then wind vs
time on the same graph. I would like the wind direction to be arrows
pointing in the designated direction (i.e. North points north).

Thank you!

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